Process control systems typically include various components for controlling various process parameters. For example, a fluid process control system may include a plurality of control valves for controlling flow rate, temperature, and/or pressure of a fluid flowing through the system. The end product is dependent on the accuracy of the control of these parameters, which is, in turn, dependent on the geometry and characteristics of the control valves. Control valves are, for example, specifically designed and selected to provide for particular flow capacities and pressure changes. When these characteristics are compromised, the quality of the end product may be affected.
To ensure that the quality of the end product is not affected, the various components of a process control system are tested during start-up, i.e., prior to being deployed for operation. For example, components such as control valves, pipelines, plumbing, gas tanks, and other pressure vessels are, prior to being deployed, typically subjected to hydrostatic testing whereby the component (e.g., the control valve, the pipeline) is filled with one or more liquids (e.g., water, oil) at room temperature (e.g., 70 degrees Fahrenheit), or another substantially similar temperature, to test the strength of the component and identify any leaks therein. In some cases, e.g., when those components are to be utilized in high-temperature environments and/or where high-pressure drops, it may also desirable to subject these components to start-up testing using fluids, e.g., steam, at or having significantly higher temperatures (e.g., temperatures in excess of 100 degrees Fahrenheit, 200 degrees Fahrenheit, 500 degrees Fahrenheit, 1000 degrees Fahrenheit, or even 1200 or 1250 degrees Fahrenheit). In yet other cases, e.g., when those components are to be utilized in extremely low-temperature environments, it may be desirable to subject these components to start-up testing using fluids at or having very low temperatures (e.g., below 70 degrees Fahrenheit, below 32 degrees Fahrenheit, cryogenic temperatures). It may also be desirable to subject these components to extremely high pressures, extremely low pressures, other pressures, and/or significant pressure drops.
However, equipment that is conventionally used to perform hydrostatic testing often includes components, e.g., rubber or plastic seals, that are not built to withstand higher temperatures, high pressure drops, and/or extremely low temperatures, such that the equipment is not operable across the whole range of temperatures and/or pressures needed to properly test the process control system component prior to operation (i.e., properly start-up test the process control system component).
FIG. 1 illustrates an example of such a conventional device, in the form of a fixture 100, which can be used to perform hydrostatic testing on a control valve 104 having a valve body 108 and a valve seat 112 disposed in the valve body 108. The fixture 100, which when employed replaces the valve plug and the valve cage of the control valve 104, includes a plug 116 and a rubber or plastic o-ring 120 arranged at one end 124 of the plug 116. The plug 116 is disposed in the valve body 108 such that a portion of the plug 116 and the o-ring 120 engage the valve seat 112. When arranged in this manner, an end user of the control valve 104 may perform hydrostatic testing on the control valve 104 and any other pressure vessels within the process control system using fluids at room temperature (e.g., 70 degrees Fahrenheit) or other similar temperatures (e.g., temperatures between 32 degrees Fahrenheit and 100 degrees Fahrenheit). But, because the o-ring 120 is made of plastic or rubber, which may extrude, disintegrate, or otherwise fail in response to temperatures in excess of 450 degrees Fahrenheit, cryogenic temperatures, high pressures, and high pressure drops, for example, the fixture 100 cannot be used for start-up testing on the control valve 104 using fluids (e.g., steam) at or having such temperatures and/or when subjected to high pressures and/or high pressure drops. As a result, the fixture 100 must be removed and different equipment used, and/or different tests employed to properly test the control valve 104, prior to operation, at such different temperatures.